Robotic endoscopic retractor for use in minimally invasive surgery

ABSTRACT

Minimaily invasive surgical retractors and methods of using the retractors are provided. This retractor may be introduced through a sealed port, controlled by a robotic system, have full articulation, and need not require assembly within the patient&#39;s body. As a result, fully endoscopic mitral valve surgery may be performed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority from U.S. provisionalpatent application Ser. No. 60/795,804, filed on Apr. 28, 2006, entitled“ROBOTIC ENDOSCOPIC RETRACTOR FOR USE IN MINIMALLY INVASIVE SURGERY,”the disclosure of which is incorporated herein in its entirety.

BACKGROUND

Mitral valve surgery has traditionally been performed through the mediansternotomy in which the left atrium of the heart is opened and exposedto allow reconstruction of the mitral valve. More recently, minimallyinvasive techniques have been used for mitral valve surgery. Minimallyinvasive techniques are aimed at reducing the amount of extraneoustissue that is damaged during diagnostic or surgical procedures, therebyreducing patient recovery time, discomfort, and deleterious sideeffects.

One minimally invasive mitral valve repair technique is illustrated inFIG. 1. After opening of the atrium, an atrial retractor 100 is used toexpose and stabilize the septum to create space for movement oflaparoscopic instruments. The atrial retractor 100 includes a retractorblade 102 and a retractor rod 104. The retractor blade is available indifferent sizes. Typically, blades which are 50 mm long and 25 to 35 mmwide are used. The retractor blade 102 is inserted through a lateralthoracotomy of sufficient size to allow the blade 102 to pass through(e.g., approximately a 3.5 to 5 cm incision). The retractor rod 104 isinserted into the thorax through an incision 108 in the second or thirdintercostal space just 2 to 3 cm laterally to the sternum in the rightchest. The retractor blade 102 is then attached to the retractor rod104, typically using a screw mechanism.

The atrial retractor is positioned in the right atrium so as to retractthe atrial wall to provide satisfactory exposure of the mitral valveannulus and subvalvular structure. The retractor rod 104 is secured inplace using a stable structure, such as a holding arm, the operatingtable, or the patient's chest.

One disadvantage of transthoracic mechanical retractors, such as theatrial retractor 100, is that a thoracotomy is still required in orderto introduce the atrial retractor, thereby preventing a fully endoscopicapproach to mitral valve repair. In addition, during a robotic assistedmitral valve operation with the da Vinci Surgical System by IntuitiveSurgical, Inc. of Sunnyvale, Calif., the insertion of the retractorblade 102, the attaching of the blade 102 and rod 104, and locking andsecuring of the rod 104 to the holding arm are typically performed whilethe robotic arm cart is docked to the patient, thereby constraining theworkspace for the patient side surgeon. The size of the blade 102 thatcan be utilized is also limited by space limitations of the thoracotomyand within the patient's body.

Furthermore, the assembly of the retractor 100 is cumbersome andcounter-intuitive. The patient side surgeon typically aligns theretractor blade 102 and the rod 104 laparoscopically. If the surgeon isnot laparoscopically trained, the assembly time and time to mitral valveexposure can be long and frustrating.

The quality of the mitral valve exposure may vary dramatically frompatient to patient, depending on where the retractor rod 104 enters thethoracic cavity. The incision serves as a fixed pivot point for therigid retractor rod 104, thereby limiting the adjustment of positioningof the retractor blade 102.

In some cases, the retractor rod 104 may collide with the robotic cameraarm, thereby decreasing the mitral valve exposure and obstructing thesurgeon's view. Moreover, once the retractor 100 is positioned,repositioning later in the procedure may be difficult or impossible.When reposition is possible, the patient side assistant will typicallyhave to perform multiple maneuvers to unlock and readjust the atrialretractor 100, which can be time consuming and cumbersome.

Finally, these retractors may introduce air into the aortic root due todistortion of the aortic valve.

Accordingly, there is a need for an improved retractor which may be usedfor minimally invasive heart valve repair and other surgical procedures.

SUMMARY

A minimally invasive surgical retractor is provided. This retractor maybe introduced through a sealed port, controlled by a robotic system,have full articulation, and need not require assembly within thepatient's body. As a result, fully endoscopic mitral valve surgery maybe performed.

In accordance with embodiments of the present invention, a minimallyinvasive surgical instrument is provided, including: an elongate shaft;and a retractor assembly coupled to a distal end of the elongate shaft,the retractor assembly comprising a pair of blades, each blade having amounting end coupled to a pivot point and an opposing free end, whereinsaid pair of blades are substantially overlapped when in a closedposition and having the opposing free ends angularly displaced from eachother when in an open position.

In accordance with embodiments of the present invention, a method ofperforming minimally invasive endoscopic surgery in a body cavity of apatient is provided, the method comprising: introducing an elongateshaft into the cavity, the elongate shaft having a proximal end, a shaftcoupled to the proximal end, a wrist assembly coupled to the shaft, anda retractor assembly coupled to the wrist assembly, said retractorassembly comprising a pair of blades, each blade having a mounting endcoupled to the wrist assembly and an opposing free end; deploying theretractor assembly inside the cavity by angularly displacing the freeends of the pair of blades; and retracting tissue using the retractorassembly.

Other features and aspects of the invention will become apparent fromthe following detailed description, taken in conjunction with theaccompanying drawings which illustrate, by way of example, the featuresin accordance with embodiments of the invention. The summary is notintended to limit the scope of the invention, which is defined solely bythe claims attached hereto.

DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a mitral valve repair procedure utilizing aconventional atrial retractor.

FIG. 2 shows a robotic surgical system including a master controlstation and a robotic arm cart.

FIG. 3 illustrates a surgical instrument, in accordance with embodimentsof the present invention.

FIGS. 4A-4C are an enlarged perspective views of the working end of thesurgical instrument, including a wrist assembly and retractor assembly.

FIGS. 5A and 5B are front and rear perspective views of an inner bladeof the retractor assembly, and FIG. 5C is a rear plan view of the innerblade.

FIGS. 6A and 6B are front and rear perspective views of an outer bladeof the retractor assembly.

FIGS. 7A-7E are various views of a portion of the wrist assembly.

FIGS. 8A-8B are enlarged views of the wrist assembly.

FIG. 9 is a simplified view of a mitral valve with an annuloplasty ringattached thereto.

FIG. 10 is a view of the retractor instrument deployed inside the leftatrium.

FIG. 11 illustrates a retractor assembly, in accordance with anotherembodiment of the present invention.

FIGS. 12A-12B are simplified views showing the possible articulation ofthe working end of the instrument.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanyingdrawings which illustrate several embodiments of the present invention.It is understood that other embodiments may be utilized and mechanical,compositional, structural, electrical, and operational changes may bemade without departing from the spirit and scope of the presentdisclosure. The following detailed description is not to be taken in alimiting sense, and the scope of the embodiments of the presentinvention is defined only by the claims of the issued patent.

Spatially relative terms, such as “beneath”, “below”, “lower”, “above”,“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

Robotic surgery systems, devices, and methods are described. Roboticsurgery will generally involve the use of multiple robotic arms. One ormore of the robotic arms will often support a surgical tool which may bearticulated (such as jaws, scissors, graspers, needle holders,microdissectors, staple appliers, tackers, suction/irrigation tools,clip appliers, or the like) or non-articulated (such as cutting blades,cautery probes, irrigators, catheters, suction orifices, or the like).One or more of the robotic arms will often be used to support one ormore surgical image capture devices such as an endoscope (which may beany of the variety of structures such as a laparoscope, an arthroscope,a hysteroscope, or the like), or optionally, some other imaging modality(such as ultrasound, fluoroscopy, magnetic resonance imaging, or thelike). Typically, the robotic arms will support at least two surgicaltools corresponding to the two hands of a surgeon and one optical imagecapture device. A fourth robotic arm may be provided to support apositionable retractor assembly, as will be described in greater detailbelow.

Positionable retractor instruments may be utilized in a variety ofsurgical procedures. The most immediate applications will be to improveexisting minimally invasive surgical procedures, such as mitral andaortic valve repair and/or replacement. Additionally, it is anticipatedthat these surgical systems will find uses in entirely new surgeriesthat would be difficult and/or impossible to perform using traditionallyopen or known minimally invasive techniques. Additional potentialapplications include vascular surgery (such as for the repair ofthoracic and abdominal aneurysms), general and digestive surgeries (suchas cholecystectomy, inguinal hernia repair, colon resection, and thelike), gynecology (for fertility procedures, hysterectomies, and thelike), and a wide variety of alternative procedures.

FIG. 2 shows a robotic surgical system 200 including a master controlstation 210 coupled to a robotic arm cart 220. The master controlstation 210 generally includes master controllers 212 which are graspedby the surgeon and manipulated in space while the surgeon views theprocedure views a stereo display. The master controllers 212 are manualinput devices which may move with six degrees of freedom, and whichoften further have an actuatable handle for actuating instruments (forexample, for closing grasping saws, applying an electrical potential toan electrode, or the like). The master control station 210 may alsoinclude a processor.

The robotic arm cart 220 is positioned adjacent to the patient's bodyand moves instruments having shafts. The shafts extend into an internalsurgical site within the patient body via openings in the body. One ormore assistants may be present during surgery to assist the surgeon,particularly during removal and replacement of instruments. Roboticsurgery systems and methods are further described in U.S. Pat. No.5,797,900, filed on May 16, 1997, issued on Aug. 25, 1998, U.S. Pat. No.6,132,368, filed on Nov. 21, 1997, issued on Oct. 17, 2000, U.S. Pat.No. 6,331,181, filed on Oct. 15, 1999, issued on Dec. 18, 2001, U.S.Pat. No. 6,441,577, filed on Apr. 3, 2001, issued on Aug. 27, 2002, U.S.Pat. No. 6,902,560, filed on Jan. 6, 2004, issued on Jun. 7, 2005, U.S.Pat. No. 6,936,042, filed on Apr. 16, 2002, issued on Aug. 30, 2005, andU.S. Pat. No. 6,994,703, filed on Dec. 4, 2002, issued on Feb. 7, 2006,the full disclosures of which are incorporated herein by reference. Asuitable robotic surgical system currently in use is the da Vinci SSurgical System by Intuitive Surgical, Inc.

The robotic arm cart 220 includes a base 222 from which four surgicalinstruments 230 are supported. More specifically, the surgicalinstruments 230 are each supported by a series of manually articulatablelinkages, generally referred to as set-up joints 232, and a roboticmanipulator 234. The robotic manipulators 234 enable the instrument 230to be rotated around a point in space, as more fully described in issuedU.S. Pat. Nos. 6,331,181, and 5,817,084, the full disclosures of whichare incorporated herein by reference. The robotic manipulators 234 pivotthe instrument 230 about a pitch axis, a yaw axis, and an insertion axis(which is aligned along a shaft of the instrument 230). The instrument230 has still further driven degrees of freedom as supported by themanipulator 234, including sliding motion of the instrument 230 alongthe insertion axis.

The robotic manipulators 234 are driven by a series of motors. Thesemotors actively move the robotic manipulators 234 in response tocommands from a processor. The motors are further coupled to theinstrument 230 so as to rotate the instrument 230 about the insertionaxis, and often to articulate a wrist at the distal end of theinstrument about at least one, and often two, degrees of freedom.Additionally, the motors can be used to actuate an articulatable endeffector of the instrument for grasping tissues in the jaws of a forcepsor the like. The motors may be coupled to at least some of the joints ofinstrument 230 using cables, as more fully described in U.S. Pat. Nos.6,331,181, and 5,792,135, the full disclosures of which are alsoincorporated herein by reference. As described in those references, themanipulators 234 will often include flexible members for transferringmotion from the drive components to the surgical instrument. Forendoscopic procedures, the manipulators 234 may include a cannula, whichsupports the instrument 230, allowing the instrument 230 to rotate andmove axially through the central bore of the cannula.

FIG. 3 illustrates a surgical instrument 300, including a shaft portion302, a control housing 303 provided at a proximal end of the shaftportion 302, and a working end 310 at a distal end of the shaft portion302. The working end 310 comprises a wrist assembly 320 coupled to aproximal clevis assembly 304 provided at a distal end of the shaftportion 302, and a retractor assembly 330 coupled to the wrist mechanism320. When the surgical instrument 300 is coupled or mounted onto therobotic manipulator 234, the shaft portion 302 extends along theinstrument axis. A similar robotic manipulator and surgical instrumentis described in U.S. Pat. No. 6,902,560, the disclosure of which isincorporated by reference herein in its entirety.

FIGS. 4A-4C are enlarged perspective views of the working end 310 of thesurgical instrument 300, including the wrist assembly 320 and retractorassembly 330. FIGS. 5A and 5B are front and rear perspective views of aninner blade 340 of the retractor assembly 330, and FIG. 5C is a rearplan view of the inner blade 340. FIGS. 6A and 6B are front and rearperspective views of an outer blade 350 of the retractor assembly 330.FIGS. 7A-7C are various perspective views and FIGS. 7D-7E are plan viewsof a portion of the wrist assembly 320. FIGS. 8A-8B are enlarged viewsof the wrist assembly 320. FIGS. 12A-12B are simplified views showingthe possible articulation of the working end 310.

The proximal clevis assembly 304 is rotatably coupled to the end 305 ofthe shaft 302 such that the proximal clevis assembly 304 is rotatableabout the axis of the shaft 302 (shown in FIGS. 12A-12B as axis R). Thisrotation of the proximal clevis assembly 304 about the shaft axis isreferred to as the roll of the assembly 304 (shown in FIGS. 12A-12B asroll R₁). One end of the wrist assembly 320 is pivotally mounted in theproximal clevis assembly 304 by means of a pivotal connection 306. Thewrist assembly 320 includes a rigid wrist member 322 which can rotateabout the pivotal connection 306 (shown in FIGS. 12A-12B as axis P).This rotation about the pivotal connection 306 is referred to as thepivot or pitch of the wrist member 322 (shown in FIGS. 12A-12B as pitchP₁).

The retractor assembly 330 serves as the end effector of the surgicalinstrument 300 and is pivotally mounted on a second pivotal connection307 provided in a distal clevis portion 308 of the wrist assembly 320.The retractor assembly 330 comprises an inner blade 340 and an outerblade 350, each including a mounting end 344, 354 pivotally mounted tothe second pivotal connection 307. The blades 340, 350 also include freeends 342, 352, which are angularly displaceable about the second pivotalconnection 307 toward and away from each other, and a body portiondisposed between the mounting end 344, 354 and the free end 342, 352. Inthis embodiment, the free ends 342, 352 are provided with a slightlycurved tip which extends at an angle relative to the plane defined bythe body of the blades 340, 350. The curved tips enable the retractorblades 340, 350 to more securely grip the cardiac tissue, as will bedescribed in greater detail below. In addition, the edges of the blades340, 350 are blunt so as to avoid causing damage to the tissue beingretracted.

FIGS. 4A and 4C show the blades 340, 350 of the retractor assembly 330displaced away from each other in the open position, while FIG. 4B showsthe blades 340, 350 of the retractor assembly 330 brought together inthe closed position. In the embodiment shown in FIGS. 4A-4C, the outerblade 350 is slightly longer than the inner blade 340 so that the curvedtip of the free end 342 of the inner blade 340 fits inside the curvedtip of the free end 352 of the outer blade 350.

The retractor blade 340 includes a pulley portion 346 which defines acircuniferentially extending channel 347 in which an elongate element inthe form of, e.g., an activation cable, is carried. In this embodiment,a cylindrical crimp member is provided medially along the activationcable. This crimp member is received in the aperture 345 of the blade340 to couple the cable and the blade 340 together.. The ends of theactivation cable are operatively coupled to a control interface providedon the control housing 303 such that linear movement of the activationcable actuates rotational movement of the blade 340. In otherembodiments, two activation cables may be used to actuate rotation ofthe blade 340.

FIGS. 6A-6B illustrate the outer blade 350, which operates insubstantially the same way as the inner blade 340. Each blade 340, 350includes a slot 348, 358 and a protruding boss 349, 359. The boss 349 onthe inner blade 340 is slidably received in the slot 359 of the outerblade 350, and the boss 359 on the outer blade 350 is slidably receivedin the slot 349 of the inner blade 340. The length of the slots 348, 358and the relative positions of the slots 348, 358 and bosses 349, 359limit the extent to which the blades 340, 350 can rotate relative toeach other. One end of the slots 348, 358 correspond to the closedposition of the blades 340, 350 and the other end of the slots 348, 358correspond to the open position of the blades 340, 350. In thisembodiment, the blades 340, 350 are configured to be angularly displacedfrom each other by a maximum of 60°. In other embodiments, the slots348, 358 may be made shorter to decrease the maximum angulardisplacement, or made longer to increase the maximum angulardisplacement.

Each side of the wrist member 322 includes a pair of offset distal idlerpulleys 324 a-324 b, which are mounted to pulley mounts 325, and a pairof pulleys 323 a-323 b, which are mounted at the pivotal connection 306between the wrist assembly 320 and the proximal clevis assembly 304. Thedistal idler pulleys 324 a-324 b and pulleys 323 a-323 b function toroute the activation cables through the wrist assembly 320 to the blades340, 350. The idler pulleys 324 a-324 b are offset so that the fleetangles of the pulleys 324 a-324 b are optimized.

The wrist member 322 includes a pulley portion 326, which defines a pairof channels 327 a-327 b in which elongate elements (e.g., activationcables) are carried. These activation cables have a distal end receivedin the opening 328 a-328 b in the wrist member 322, and a proximal endoperatively coupled to the controller interface of the controllerhousing 303. Alternatively, a single activation cable may be used,whereby a median portion of the cable is coupled to the wrist member 322and the distal ends of the cable are operatively coupled to thecontroller interface.

A plurality of elongate elements, e.g., activation cables, are used toeffect movement of the wrist assembly 320 and the retractor assembly330. The activation cables pass from the wrist assembly 320 throughappropriately positioned holes in the base region of the proximal clevisassembly 304, and internally along the shaft 302, toward the housing303. The housing 303 includes a controller interface comprising drivingmembers, e.g., in the form of spool assemblies for manipulating theactivation cables. Additional details of a similar mechanisms formanipulating various surgical tools, including control housings andspool assemblies, can be found in U.S. Pat. No. 6,394,998, filed on Sep.17, 1999, issued on May 28, 2002, and U.S. Pat. No. 6,902,560, filed onJan. 6, 2004, issued on Jun. 7, 2005, the disclosures of which areincorporated by reference herein in their entireties.

The various components of the surgical instrument 300, and, inparticular, the wrist assembly 320 and the retractor assembly 330, maybe fabricated from surgical grade stainless steel. In the illustratedembodiment, each of the blades 340, 350 of the retractor assembly 330have a width of approximately 6.6 mm and a thickness of approximately1.77 mm. In addition, the edges along the length of the blades 340, 350are curved at a radius of approximately 1.75 mm, the corners at the endportions are curved at a radius of approximately 2.5 mm, and the endportion 342 of the inner blade 340 is curved inward such that the innersurface has a radius of curvature of approximately 1.4 mm. In thisembodiment, the outer blade 350 is slightly longer than the inner blade340. Exemplary dimensions for the outer blade 350 are shown in FIG. 5C.The inner blade 340 is approximately 2 mm or 0.08 inches shorter inlength. FIG. 7D shows exemplary dimensions in inches for the wristmember 322. In other embodiments, the blades 340, 350, wrist member 322,and other components of the instrument 300 may be provided in differentsizes and all of the dimensions may vary. In particular, it may bedesirable for a manufacturer to provide retractor instruments in avariety of effective lengths, such as 35 mm, 40 mm, or 50 mm, so as toaccommodate a variety of patient anatomies. The effective length of theblades 340, 350 is measured from the end of the wrist member 322 to thetip of the distal ends 342, 352.

When the blades 340, 350 are in the closed position, the blades 340, 350are substantially overlapped so that the entire retractor assembly 330has a closed width approximately equal to the diameter of the shaft 302,which can be, e.g., 8 mm. This enables the retractor assembly 330 to beinserted through small-diameter cannula sleeves (e.g., 8.5 mm innerdiameter cannula sleeves) to the internal surgical site. In theillustrated embodiment, the blades 340, 350 have substantially identicalwidths which are substantially constant along the length of the blades.This differs with scissor tools, which typically have blades that narrowtowards the tips so as to minimize the surface area to improve the easewith which the scissors may be operated to cut through tissue and othermaterials. In contrast, the constant width of the blades 340, 350maximizes the size of the blade surface for use in retracting tissuewhen opened, while still enabling the insertion of the closed blades340, 350 through the cannula. In this embodiment, the blades 340, 350,have a substantially rectangular profile, with curved end portions 342,352, which reduce the risk of tissue damage that may be caused by sharpcorners. In addition, the low profile and thinness of the retractorblades 340, 350 conceal only a small portion of atrial tissue whendeployed. This may result in greater exposure along with less absorptionof light.

An application of the retractor instrument 300 will be described below.In this embodiment, the robotic surgical system 200 comprises the daVinci S Surgical System. Two articulated instrument arms and athree-dimensional high-magnification 30° camera were port-introducedinto the right thorax of the patient. A fourth instrument arm isprovided with the retractor instrument 300, described above. This fourthinstrument arm allows for six degrees of freedom of movement, inaddition to adjustable separation of the end portions 342, 352 of theretractor blades 340, 350. The retractor instrument 300 is introducedinto the chest via a 10-mm trocar.

FIG. 10 is a view of the retractor instrument 300 deployed inside theleft atrium. After the retractor wrist assembly 320 is visible withinthe thorax by the console surgeon, the console surgeon positions andspreads the blades 340, 350 inside the left atrium. To reposition theblades 340, 350, the surgeon may toggle control back and forth betweenthe instrument arm and retractor arm using the foot pedal clutch of theda Vinci system. The retractor blades 340, 350 are then separated gentlyand the tips positioned near each fibrous trigone. By reactivating theinstrument arm with the clutch, the atrial retractor 300 remains inposition and leaflet repairs may be performed using the two instrumentarms.

Upon completion of leaflet repairs and subvalvular work, the blades 340,350 may be repositioned to optimize exposure of the right fibroustrigone and posterior commissure for annuloplasty band insertion usingeither sutures or nitinol clips. Generally, a third maneuver is utilizedfor optimal access of the left fibrous trigone and anterior commissure.Before removing the device and closing the atrium, the retractor blades340, 350 may be lowered to establish normal atrial geometry for salinetesting in order to assess valve competency.

In accordance with aspects of the present invention, dynamic atrialretraction may be provided in order to provide different exposure viewsbased on surgical needs. FIG. 9 is a simplified view of a mitral valve900 with an annuloplasty ring 930 attached thereto. In order to attachthe ring 930 to the annulus 912 of the valve 900, the surgeon must haveexposure to the trigones to which the ring 930 is attached. Due to thelimited viewing angle of the imaging system, only a portion of theannulus 912 may be visible at any point during the procedure. Forexample, in order to attach the ring 930 to the left trigone, it may bedesirable to provide a first view 902. After the attachment is complete,it would be desirable to reposition the imaging system to provide asecond view 904 of the right trigone. Conventional retractors may not beable to provide optimal views of both the left and right trigones. Incontrast, the retractor instrument 300 may be repositioned during theprocedure so as to provide optimal exposure of the region currentlybeing imaged by the surgeon.

In accordance with other embodiments of the present invention, differentretractor blade geometries and configurations may be used. For example,FIG. 10 illustrates a retractor assembly 1030, in accordance withanother embodiment of the present invention. The retractor assembly 1030includes two rotatable blades 1040, 1050 supporting an expansionstructure 1060. The blades 1040, 1050 have a proximal end rotatablycoupled to a pivotal connection 1070 and distal ends 1042, 1052 whichare angularly displaceable about the pivotal connection 1070. As thedistal ends 1042, 1052 are angularly displaced, the expansion structureexpands to the open configuration shown in FIG. 11. This configurationserves to provide a large surface region for retracting tissue.

In accordance with other embodiments of the present invention, anon-rigid webbing may be provided between the retractor blades so as toenable the capture of a greater amount of tissue and prevent tissue fromprotruding between the blades. This webbing may comprise a net or meshwhich is coupled to the blades such that when the blades are in theclosed position, the webbing is collapsed and may pass through thecannula. When the blades are in the open position, the webbing isexpanded to provide a large surface area.

Embodiments of the present invention may provide various advantages notprovided by prior art systems. The overall size of the retractorassembly 330 may be substantially equal to existing instruments forminimally invasive surgery, such as the EndoWrist instruments byIntuitive Surgical, Inc. This can enable the instrument to be used withexisting equipment.

In addition, the retractor assembly 330 may be deployed within thethoracic cavity through a sealed cannula (e.g., through an 8-mm to 12-mmport). As a result, CO₂ insufflation is maintainable, thereby allowingan endoscopic procedure. 100551 Due to the curved end portions of theretractor blades, the septum and left atrium may be maintained in astable position without slipping during the duration of the mitral valveprocedure. In other embodiments, the curved end portions of theretractor blades may be longer or shorter than the end portions shownand described herein. For example, longer curved end portions may enablethe surgeon to achieve a more secure grasp of the atrial tissue. Iflonger curved end portions are used, the angle of curvature may bedecreased so as to permit the retractor assembly to pass through thesame size cannula.

Furthermore, the retractor assembly 330 allows safe and stable exposureof the mitral valve when introduced through a port in a 5 cm×10 cmsurface area lateral to the sternum, thereby making the quality of themitral valve exposure less dependent on port location.

The retractor assembly 330 may enable dynamic atrial retraction forexposure during complex procedure steps of the valve reconstructionprocedure (e.g., annuloplasty ring placement) in an endoscopicenvironment. The retractor instrument 300 may be fully articulating forflexibility in exposing the mitral valve in multiple planes.

Finally, the retractor instrument 300 may be provided as a singlepreassembled device, eliminating the need to assemble the retractorwithin the patient after insertion.

The above-described arrangements of apparatus and methods are merelyillustrative of applications of the principles of this invention andmany other embodiments and modifications may be made without departingfrom the spirit and scope of the invention as defined in the claims. Forinstance, the robotic arms may have other configurations. Differentactuation mechanisms other than activating cables may be used tomanipulate the wrist member and end effector. The scope of the inventionshould, therefore, be determined not with reference to the abovedescription, but instead should be determined with reference to theappended claims along with their full scope of equivalents.

In addition, in the illustrated embodiment, the blades 340, 350 open orclose in unison. However, in other embodiments, each of the blades 340,350 may be configured to be angularly displaced independently of theother blade 340, 350, thereby enabling a wider variety of deploymentconfigurations. In addition, in some embodiments, the wrist assembly 320is configured for pitch and roll movement only, while the retractorassembly 330 is configured for opening and closing movement only. Inother embodiments, the surgical instrument 300 may have greater or fewerdegrees of movement. In particular, in some embodiments, the retractorassembly 330 may be further configured for yaw and/or roll movement. Forexample, in the illustrated embodiment, the blades 340, 350 can rotatetogether about the pivotal connection 307 (shown in FIG. 12A as axis Y).This joint rotation of the blades 340, 350 about the axis Y is referredto as the yaw of the blades 340, 350.

Therefore, it should be understood that the invention can be practicedwith modification and alteration within the spirit and scope of theappended claims. The description is not intended to be exhaustive or tolimit the invention to the precise form disclosed. It should beunderstood that the invention can be practiced with modification andalteration and that the invention be limited only by the claims and theequivalents thereof.

1. A minimally invasive surgical instrument, comprising: an elongateshaft; and a retractor assembly coupled to a distal end of the elongateshaft, the retractor assembly comprising a pair of blades, each bladehaving a mounting end coupled to a pivot point and an opposing free end,wherein said pair of blades are substantially overlapped when in aclosed position and having the opposing free ends angularly displacedfrom each other when in an open position.
 2. The minimally invasivesurgical instrument of claim 1, further comprising: a wrist assemblyprovided between the retractor assembly and the elongate shaft, saidwrist assembly being configured to rotate around a shaft axis defined bythe elongate shaft.
 3. The surgical instrument of claim 1, wherein: saidpair of blades has substantially equal widths.
 4. The surgicalinstrument of claim 1, wherein: each blade of said pair of blades has asubstantially constant width.
 5. The surgical instrument of claim 1,wherein: each blade in the pair of blades comprises a planar bodyportion between the mounting end and the free end.
 6. The surgicalinstrument of claim 5, wherein: the free end of each blade in the pairof blades has a tip extending at an angle relative to the plane of thebody portion.
 7. The surgical instrument of claim 5, wherein: the planarbody portion of each blade has a substantially constant width.
 8. Thesurgical instrument of claim 1, wherein: each blade in the pair ofblades has a pulley portion including a circumferentially extendingchannel; said instrument further comprising: a pair of activation cablesextending through the elongate shaft, each of said activation cableshaving a distal end received in the circumferentially extending channelof one of the pair of blades and coupled to the one of the pair ofblades such that axial movement of the activation cables results inrotational of the one of the pair of blades about the pivot point. 9.The surgical instrument of claim 1, wherein: each blade in said pair ofblades has a width substantially equal to a width of the shaft.
 10. Thesurgical instrument of claim 1, wherein: each blade in said pair ofblades has a width less than 5% smaller than a width of the shaft. 11.The surgical instrument of claim 1, wherein: each blade in said pair ofblades has a width less than 10% smaller than a width of the shaft. 12.The surgical instrument of claim 1, wherein: each blade in said pair ofblades has a substantially rectangular profile.
 13. The surgicalinstrument of claim 1, wherein: each blade in said pair of blades has acurved edge so as to prevent cutting of tissue by the edge of the blade.14. A method of performing minimally invasive endoscopic surgery in abody cavity of a patient, the method comprising: introducing an elongateshaft into the cavity, the elongate shaft having a proximal end, a shaftcoupled to the proximal end, a wrist assembly coupled to the shaft, anda retractor assembly coupled to the wrist assembly, said retractorassembly comprising a pair of blades, each blade having a mounting endcoupled to the wrist assembly and an opposing free end; deploying theretractor assembly inside the cavity by angularly displacing the freeends of the pair of blades; and retracting tissue using the retractorassembly.
 15. The method of claim 14, wherein: each blade in said pairof blades has a width substantially equal to a width of the shaft. 16.The method of claim 14, wherein: each blade in said pair of blades has awidth less than 5% smaller than a width of the shaft.
 17. The method ofclaim 14, wherein: each blade in said pair of blades has a width lessthan 10% smaller than a width of the shaft.
 18. The method of claim 14,wherein: each blade in said pair of blades has a substantiallyrectangular profile.
 19. The method of claim 14, wherein: each blade insaid pair of blades has a curved edge so as to prevent cutting of tissueby the edge of the blade.